U.S. Pat. No. 4,421,075 maintains a diesel engine at a ready to start temperature by terminating the fuel supply of a running engine when the engine block temperature rises to a first predetermined value, and by starting the engine when the engine block temperature falls below a second predetermined value. U.S. Pat. Nos. 4,419,866 and 4,878,465 teach starting and stopping an internal combustion engine connected to a compressor in a transport refrigeration system, stopping the engine by cutting off the fuel supply when a conditioned space does not require cooling or heating to hold the temperature thereof in a range close to a selected set point temperature, and starting the engine when the conditioned space requires heating or cooling. My U.S. Pat. No. 5,072,703 teaches starting, running, and stopping a truck engine as required to maintain a truck sleeper unit in a desired temperature range, cutting off the fuel supply to stop the engine, and starting the engine when the sleeper unit requires cooling or heating.
In order to save fuel, reduce engine wear, and limit unnecessary emissions from internal combustion engines, such as engines on trucks, tractors, fork lifts, off-road vehicles, and the like, it would be desirable to automatically limit idling time, shutting off an engine which has been idling for a predetermined period of time when it is in a condition that it may be restarted. However, simply terminating the fuel supply of the engine, as in the U.S. patents listed above, would not be desirable when the engine may not be restarted for a relatively long period of time, as an electrical load connected to the vehicle power supply may soon discharge the vehicle battery to the point where restarting may not be possible.